An exhaust gas recirculation (EGR) system is a system which returns a portion of exhaust gases produced by an engine to the engine's air intake passage. The EGR system acts to maintain a desired air/fuel ratio in the engine cylinders, and to reduce the formation of emissions such as oxides and nitrogen.
The EGR system utilizes an EGR control valve which controls the amount of recirculated exhaust gas which enters the engine's induction system. In many EGR systems, the EGR control valve comprises a vacuum-actuated flow valve. Alternatively, the EGR valve may comprise a solenoid-driven, or solenoid-actuated valve. However, the use of a solenoid valve actuator in combination with an EGR valve may result in an increase in total valve hysteresis due to mechanical friction caused by misalignments. The increase in total valve hysteresis is caused by the two inherent mechanical misalignments of the individual devices (namely, the solenoid actuator and the EGR valve) along with the increased overall stem assembly length.